L.C. Freitas

Stand-alone photovoltaic energy storage system with maximum power point tracking

This digests deals with the study of a stand-alone photovoltaic system, which is able to extract the maximum power from photovoltaic array for all solar intensity conditions and to provide output voltage regulation. The proposed system consists of a DC-DC converter in combination with battery energy storage in a simple structure. Operating principle and control strategy are described. Digital simulation is included, supporting the validity of the concept.

A DC-DC converter adequate for alternative supply system applications

The proposed DC-DC system introduced in this work provides output voltage regulation and control of energy flow between a battery bank and the output DC bus. A simple structure, composed by a DC-DC converter and a battery energy storage, is able to compensate power and voltage fluctuations in supply grid and to provide protection against power outages. The proposed system operates in various modes of operation, according to load needs and supply grid limitations, and is suitable for alternative system applications. A general concept is formulated. Operating principle and theoretical analysis are described. Digital simulation and experimental results of a 1.5 kW, operating at 50 kHz are included for different modes of operation, supporting the validity of the concept.

Proposal of a DC-DC converter with wide conversion range used in photovoltaic systems and utility power grid for the universal voltage range

This paper describes the design and implementation of a Boost connected in cascade with a Quadratic Buck converter, with just one active switch, used to drive a LED string for public and private lighting purposes. The proposed converter supports a wide input voltage range that makes it possible to be supplied from 12 VDC to 340 VDC (240 VAC), without any additional adjustment. It can be used in hybrid electrical systems supplied by photovoltaic systems or 110/220 VAC from the utility power grid. Experimental results from an 11 W prototype are also presented.

A lossless commutation pulse width modulated converter by using a resonant disconnecting circuit

The authors describe a lossless commutation buck pulse-width-modulated converter that uses a resonant disconnecting circuit (buck-LC-PWM-RDC). The operation principle, design-oriented analysis, numerical simulation, and experimental results are presented. The topology presents a novel working mode. This is obtained by using a resonant commutation cell composed of three switches, two capacitors, and two inductors. The three switches commutate under zero current, zero voltage, and zero current, respectively. The most important property of the circuit is the ability to regulate output power and voltage by pulse-width-modulation, with constant operating frequency, without load limitation, and without sacrificing the lossless commutation. As a consequence, the time response is improved, and the design procedure and implementation are facilitated.<<ETX>>

A New Electronic Ballast used to Drive one or more High-Pressure Sodium Lamps with Voltage Synthesized Waveform

This paper presents a new electronic ballast topology used to feed one or more high pressure sodium lamps and it is ideal for poles luminaries with one or more HPS lamps used in private or public lighting. The proposed ballast supplies the lamps using synthesized waveform with fundamental frequency below 1 kHz in order to avoid acoustic resonance and minimize luminous flux oscillation. Control strategy, design guide line and experimental results are also included in this paper proposal.

A study of a soft switched bang-bang current controlled inverter

The paper presents results of operation of a soft switched bang-hang three phase current controlled inverter, aiming to obtain a nearly perfect sinusoidal current waveform as required for good torque profile and precise torque control of rotating field AC machines. Inverter devices are IGBTs switching at 40 kHz. A detailed analysis of the circuit operation is presented. The feasibility of the proposed scheme is experimentally verified on a prototype.

A soft switched current controlled converter for induction machine driving

The paper proposes a current controlled inverter operating in the ZVS mode for an induction machine drive. Operation with no voltage stress in the DC link bus is achieved. Together with the soft switching operation, a fixed frequency bang bang current control technique is also implemented, allowing for an accurate shaping of sinusoidal currents to feed the motor. As a result, a ripple free torque profile in steady-state operation is reached. With soft switching, it is possible to operate conventional IGBTs at 40 kHz. A detailed analysis of the circuit operation is presented. The feasibility of the proposed scheme is experimentally verified on a prototype.

Proposal of a dc-dc converter with wide conversion range used in photovoltaic systems and utility power grid for the universal voltage range

This paper describes the design and implementation of a Boost connected in cascade with a Quadratic Buck converter, with just one active switch, used to drive a LED string for public and private lighting purposes. The proposed converter supports a wide input voltage range that makes it possible to be supplied from 12 VDC to 340 VDC (240 VAC), without any additional adjustment. It can be used in hybrid electrical systems supplied by photovoltaic systems or 110/220 VAC from the utility power grid. Experimental results from an 11 W prototype are also presented.

A high power factor doubler half bridge boost without losses of commutation

This paper presents a high power factor doubler half bridge boost converter without Commutation Losses converter to obtain high output voltages (600 V to 900 V). A detailed analysis of its functioning is presented. Simulation and experimental results of the proposed topology are presented to confirm the ideas proposed.

A proposal of a high performance controller for a single phase inverters with internal state feedback

The purpose of this paper is to show a high performance digital control technique of single phase inverters with internal state feedback. The study proves that the high speed processor allows an excellent output signal waveform, even in critical conditions. The reduced computational effort is an attractive feature. That is obtained by using fixed-point arithmetic and proportional integral compensators.